Drive system

ABSTRACT

A drive system for use in a bicycle or the like, which includes a manually-operable member and a drive train connected to the member for transferring drive from the member to at least one of the bicycle wheels. The member is mounted for substantially rectilinear reciprocating movement on a lever system having a first lever, a second lever and a tie rod. The first lever has a first end connected to a first pivot and a second end that is rotatable about the first pivot. The second lever has a first end that is pivotably connected to the second end of the first lever and a second end to which the manually-operable member is attached. As for the tie rod, it has a first end pivotably connected to the a second pivot and a second end that is pivotably connected to the second lever between the first and second ends thereof. The first lever is constructed and arranged for limited reciprocating rotation of the second end about the first pivot.

[0001] The present invention relates to a drive system and inparticular, but not exclusively, to a drive system for a bicycle. Thedrive system is also applicable to other human-powered vehicles andmechanisms. The invention also relates to a bicycle having a drivesystem.

[0002] The drive system used by conventional bicycles consists of a pairof rotating pedal cranks connected by a chain and sprockets to the rearwheel. This system has certain disadvantages. In particular, thetangential force the cyclist is able to exert on the pedals variesconsiderably according to the positions of the pedal cranks and is at amaximum only when the pedal cranks are approximately horizontal. Thislimits the efficiency and/or maximum power output of the cyclist.

[0003] DE 4404831 A describes a drive system including a drive link thatis coupled by bearings to a crank and a tie rod. Drive is transmittedfrom the drive link through the crank to the wheels of a bicycle.

[0004] WO 96/22911 describes a drive mechanism for a bicycle, in whichthe pedals are attached to racks mounted for reciprocating movement.

[0005] It is an object of the present invention to provide a drivesystem that mitigates the aforementioned disadvantage. A further objectof the present invention is to provide a bicycle having a drive systemthat enables the cyclist to provide a greater power output and/or tocycle more efficiently.

[0006] According to the present invention there is provided a drivesystem suitable for use in a bicycle, said drive system including amanually-operable means and a drive train connected to themanually-operable means for transferring drive from themanually-operable means to at least one of the bicycle wheels, whereinthe manually-operable means is mounted for substantially rectilinearreciprocating movement on a lever system that includes a first leverhaving a first end connected to a first pivot and a second end that isrotatable about the first fixed pivot, a second lever having a first endthat is pivotably connected to the second end of the first lever and asecond end to which the manually-operable means is attached, and a tierod having a first end that is pivotably connected to a second pivot anda second end that is pivotably connected to the second lever between thefirst and second ends thereof; characterised in that the first lever isconstructed and arranged for limited reciprocating rotation of thesecond end about the first pivot.

[0007] Although the drive system is suitable for use in a bicycle, itmay also be used for driving other vehicles or mechanisms. It is notintended that the present invention is limited to drive systems forbicycles. The lever system produces the substantially rectilinearreciprocating movement of the manually-operable means, and is veryefficient in operation.

[0008] The manually-operable means is preferably a pedal or a pair ofpedals, although it may alternatively be a handle. Mounting themanually-operable means for substantially rectilinear reciprocatingmovement allows a very efficient input of energy into the drive systemfrom the user, avoiding the inefficiencies of traditional rotating cranksystems. A bicycle equipped with the drive system can therefore beridden more quickly and/or with less effort.

[0009] Advantageously, the drive system includes two lever systems thatare interconnected for opposed reciprocating movement, each lever systemincluding a manually-operable means. This allows both feet, or bothhands, to be used to drive the system with alternating strokes.

[0010] The drive system may include a hydraulic drive pump that isconnected to a third pivot and to the first lever between the first andsecond ends thereof, for actuation by pivoting movement of the firstlever. The system may also include an adjuster device for adjusting theposition of the third pivot relative to the first pivot, to adjust thestroke length of the cylinder. Advantageously, the adjuster device is ahydraulic adjuster. The hydraulic drive pump may be connected through ahydraulic circuit to a hydraulic motor.

[0011] The use of a hydraulic drive train allows drive to be transferredefficiently to the wheels, while adjusting stroke length of thehydraulic pump provides a simple method of adjusting the gearing effectof the drive system. If a hydraulic adjuster is used, an automatic orsemi-automatic gearing system can be provided. While a hydraulic drivetrain is preferred, the drive train may alternatively be entirelymechanical.

[0012] In an alternative preferred form of the invention, themanually-operable means is attached to a shaft that is mounted for axialreciprocating movement. Advantageously, the system includes a pair ofshafts mounted substantially parallel to one another for axialreciprocating movement, each said shaft having a manually-operable meansattached thereto. The shafts are preferably interconnected for opposedreciprocating movement.

[0013] This system also produces the substantially rectilinearreciprocating movement of the manually-operable means, and is veryefficient in operation. The use of two parallel shafts that areinterconnected for opposed reciprocating movement allows both feet, orboth hands, to be used to drive the system with alternating strokes.

[0014] Advantageously, the shafts are drivingly connected to a sub-shaftthat is mounted for axial reciprocating movement, and are preferablymounted substantially perpendicular to the sub-shaft. The sub-shaft maybe connected to a hydraulic drive pump, which may be connected through ahydraulic circuit to a hydraulic motor. The use of a hydraulic drivetrain allows drive to be transferred efficiently to the wheels.

[0015] Advantageously, the hydraulic drive motor is a variable capacitymotor, which allows the gearing effect of the drive system to beadjusted.

[0016] Advantageously, the drive system includes a plurality ofhydraulic motors and means for connecting the motors into the hydrauliccircuit individually, in series or in parallel, to adjust the gearingeffect of the drive system.

[0017] According to another aspect of the present invention there isprovided a bicycle having a drive system as described in the precedingparagraphs.

[0018] The bicycle may includes a hydraulic drive train including atleast one hydraulic motor for driving the rear wheel, the front wheel orboth wheels of the bicycle. The bicycle may include a plurality ofhydraulic motors that can be connected into the hydraulic circuitindividually, in series or in parallel to adjust the gearing effect ofthe drive system.

[0019] Embodiments of the invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

[0020]FIG. 1 is side view of a first embodiment of the drive system;

[0021]FIG. 2 is a side view of a bicycle having a drive system as shownin FIG. 1;

[0022]FIG. 3 is a hydraulic circuit diagram of a hydraulic drive trainfor use with the drive system;

[0023]FIG. 4 is an isometric view of a second embodiment of the drivesystem;

[0024]FIG. 5 is a front view of the second drive system;

[0025]FIG. 6 is a side view of the second drive system, and

[0026]FIG. 7 is a top view of the second drive system, and

[0027]FIG. 8 is a sectional view of a variable displacement motorforming part of the drive system.

[0028] The invention relates to a drive system for bicycles or otherpedal driven mechanisms. The system includes a first arm 1 and a secondarm 2, which are attached to the bicycle frame 3 at their upper endsthrough first and second pivots 4,5. A lever 6 is attached to the lowerends of the first and second arms through third and fourth pivots 7,8,the third pivot 7 being located at one end of the lever 6 and the fourthpivot 8 being located between the ends of the lever, close to the thirdpivot 7. A pedal 9 is attached to the free end of the lever 6, thearrangement being such that the pedal can move up and down substantiallylinearly, as indicated by the arrow labelled “down”. All these items maybe duplicated in a symmetrical fashion for a second pedal.

[0029] The first arm 1 is attached to a drive train to turn the wheelsor drive the mechanism. In a preferred arrangement of the design thedrive train consists of a hydraulic drive cylinder 10, which is attachedat its lower end to a pivot 11 on the first arm 1, located between itsends. The hydraulic drive cylinder 10 is attached at its upper end tothe frame 3 and a hydraulic adjuster 12. The hydraulic adjuster 12 isalso attached to the frame 3 through a pivot 13 and may be actuated toadjust the position of the upper end of the drive cylinder relative tothe frame. The hydraulic drive cylinder pumps oil around a hydraulicsystem. This system which is shown in FIG. 3, has an oil reservoir 15and a regulation system and a control system 16 and one or morehydraulic motors 17.

[0030] When a pressure is exerted on the pedal 9 the lever 6 moves inthe direction labelled “down” and rotates around pivot 7 and thereaction through the second arm 2 forces the first arm 1 to rotatearound pivot 4, driving the hydraulic drive cylinder 10, which isarranged to pump oil around the hydraulic system. When the pedal 9reaches the end of possible movement it is so arranged to return to thestart position at the opposite end of its range of movement. In so doingthe hydraulic drive cylinder 10 is refilled with fluid and the cyclestarts again. The components are so arranged that movement of thehydraulic adjuster 12 has the effect of varying the amount of oil pumpedaround the system, thereby providing a continuously (i.e. steplessly)variable gearing system. The adjuster may be arranged in such such a waythat the fluid in the drive system operates the adjuster so providingautomatic adjustment of the gear ratios. Both sides may be connectedtogether to ensure that the pedals move in opposite directions.

[0031] The hydraulic circuit may be arranged as shown in the diagramincluded here for clarity only. Fluid is drawn from the reservoir 15through a one way valve 18 to the hydraulic cylinder 10 and pumped underpressure through another one way valve 19 to the control system 16 andso through motors 17 as required then returning to the reservoir. Asmall amount of fluid is passed into a second control system 20 toactuate the adjuster 12.

[0032] In alternative arrangements, the hydraulic components may bereplaced by a gear, shaft or chain drive. In these arrangementsprovision will be made for relative movement of the pivots to provide arange of gear ratios.

[0033] The constituent parts are so arranged that the movement of thepedal and output is in relation to the force that can be exerted on thepedal. There is no point in the cycle that a full force cannot be outputby the system. By aligning the direction of pedal movement with theinput force the system makes more efficient use of the work energyavailable.

[0034] Various modifications of this drive system are possible. Forexample, the drive cylinder may be connected to the second arm insteadof the first arm; the lever to which the pedal is attached may be curvedrather than straight; and the whole mechanism may be orienteddifferently, for example when it is advantageous for the personoperating the drive system to adopt a reclined position.

[0035] An alternative drive system is shown in FIGS. 4 to 7. In thissystem, the pedals 30 are attached to the lower ends of two parallelpedal shafts 32, which are mounted for axial movement in a housing 34and are connected to a hydraulic drive piston 36 through a pair oftransfer gears 3 8 and a piston shaft 40. The housing is shown in FIG. 6but is omitted from the other figures for clarity.

[0036] Each pedal shaft 32 is provided on one face with a gear rack 42:in the embodiment shown in the drawings the rack is provided on the rearface of the left-hand pedal shaft and on the front face of theright-hand pedal shaft.

[0037] The transfer gears 38 are mounted in the housing 34 with theiraxes perpendicular to the axes of the pedal shafts 32. Each transfergear includes a large radius gear 44 at its outer end, which engages therack 42 on the associated pedal shaft, and a smaller radius gear 46 atits inner end, which engages an associated gear rack 48 on the upperside of the piston shaft 40.

[0038] The piston shaft 40 is mounted for axial movement in the housing34 and is connected at one end to the hydraulic drive piston 36, whichwith a cylinder 50 forms a hydraulic drive pump 52. The drive pump 52 isconnected through a hydraulic circuit to a drive motor. The drive motormay be a variable displacement motor, to provide a gearing effect.

[0039] To operate the drive system, the pedals 30 are pushed upwards anddownwards by the rider, causing the pedal shafts 32 to reciprocate. Thisreciprocating movement is transferred to the piston shaft 40 by thetransfer gears 38, which also increase the force and reduce theamplitude of the movement. This drives the hydraulic pump 52, which inturn drives the motor.

[0040] A suitable variable displacement motor 54 is shown in FIG. 8. Themotor 54 includes a rotor 56 that is hexagonal in cross-section and hassix cylinders 57 around its circumference, in each of which is mounted apiston 58. The rotor 56 is mounted for rotation on a fixed,non-rotatable shaft 60 having a shaft axis 61. The six pistons 58slidingly engage the inner hexagonal walls 62 of an outer housing 64,which is mounted on a mounting plate (not shown) for rotation about ahousing axis 65 with the rotor 56, and is drivingly connected to one orboth of the bicycle wheels.

[0041] Sealing walls 66 are provided on the shaft 60, which divide theannular gap 67 between the shaft and the rotor 56 into two halves. Oilis fed to and drained from each half of this gap through an oil inletopening 68 and an oil outlet opening 70 in the shaft 60. Vents 72 in therotor 56 extend between the gap 67 and the cylinders 57, allowing oil todrive the pistons 58.

[0042] The shaft 60 is mounted on an eccentric 73 having an axis ofrotation 74, which can be rotated to vary the separation between theshaft axis 61 and the housing axis 65. This allows the swept volume ofthe pump 54 to be varied, thereby adjusting the torque and the gearingratio. Rotation of the eccentric may be limited by stops (not shown).

[0043] In operation, oil is supplied under pressure through the inletopening 68 into the gap 67 between the shaft 60 and the rotor 56, andpasses through the vents 72 into the three cylinders 57 located on theinlet side of the gap 67, so driving the pistons 58 in those cylindersoutwards. At the same time, oil is exhausted from the three cylinders onthe outlet side of the gap 67 and escapes through the outlet opening 70.The unbalanced force generated by the pistons creates a turning momenton the rotor, owing to the separation between the shaft axis 61 and thehousing axis 65. The rotor 56 and the housing 64 therefore rotate aboutthe shaft 60, driving the wheel or wheels of the bicycle.

[0044] By rotating the eccentric 73, the separation between the shaftaxis 61 and the housing axis 65 can be varied to adjust the torque andgearing ratio. Rotation of the eccentric 73 may be controlled manuallyor automatically (for example, mechanically or hydraulically) to providea self-regulating drive system.

[0045] Various modifications of the drive system are possible. Forexample, in the embodiment shown in the drawings, the transfer gears 38are arranged to engage gear racks on opposite sides of the two pedalshafts 32, so that the pedals 30 move in opposite directions.Alternatively they can be arranged to engage gear racks on the same sideof the two pedal shafts 32, and on opposite sides of the pump shaft 40,to produce the same effect It is also possible to mount both transfergears on a single shaft, which has its axis situated diagonally withrespect to the gear rack on the pump shaft.

1. A drive system suitable for use in a bicycle, said drive systemincluding a manually-operable means (9) and a drive train connected tothe manually-operable means for transferring drive from themanually-operable means (9) to at least one of the bicycle wheels,wherein the manually-operable means is mounted for substantiallyrectilinear reciprocating movement on a lever system that includes afirst lever (1) having a first end connected to a first pivot (4) and asecond end (7) that is rotatable about the first pivot, a second lever(6) having a first end that is pivotably connected to the second end ofthe first lever (1) and a second end to which the manually-operablemeans (9) is attached, and a tie rod (2) having a first end that ispivotably connected to a second pivot (5) and a second end that ispivotably connected to the second lever between the first and secondends thereof; characterised in that the first lever (1) is constructedand arranged for limited reciprocating rotation of the second end aboutthe first pivot (4).
 2. A drive system according to claim 1, wherein themanually-operable means (9) is a pedal.
 3. A drive system according toclaim 1 or claim 2, including two lever systems that are interconnectedfor opposed reciprocating movement, each lever system including amanually-operable means (9).
 4. A drive system according to claim 3,including a hydraulic drive pump (10) that is connected to a third pivotand to the first lever (1) between the first and second ends thereof,for actuation by pivoting movement of the first lever.
 5. A drive systemaccording to claim 4, including means (12) for adjusting the position ofthe third pivot relative to the first pivot, to adjust the stroke lengthof the cylinder.
 6. A drive system according to claim 5, including ahydraulic adjuster (12) for adjusting the position of the third pivot.7. A drive system according to anyone of claims 4 to 6, wherein saidhydraulic drive pump (10) is connected through a hydraulic circuit to ahydraulic motor (17).
 8. A drive system suitable for use in a bicycle,said drive system including a manually-operable means (30) and a drivetrain connected to the manually-operable means for transferring drivefrom the manually-operable means to at least one of the bicycle wheels,wherein the manually-operable means (30) is mounted for substantiallyrectilinear reciprocating movement, wherein said manually-operable meansis attached to a shaft (32) that is mounted for axial reciprocatingmovement.
 9. A drive system according to claim 8, wherein themanually-operable means (30) is a pedal.
 10. A drive system according toclaim 8 or claim 9, including a pair of shafts (32) mountedsubstantially parallel to one another for axial reciprocating movement,each said shaft having a manually-operable means (30) attached thereto.11. A drive system according to claim 10, wherein said shafts (32) areinterconnected for opposed reciprocating movement.
 12. A drive systemaccording to claim 10 or claim 11, wherein said shafts are drivinglyconnected to a sub-shaft (40) that is mounted for axial reciprocatingmovement.
 13. A drive system according to claim 12, wherein said shafts(32) are mounted substantially perpendicular to the sub-shaft (40). 14.A drive system according to claim 12 or claim 13, wherein said sub-shaft(40) is connected to a hydraulic drive pump (52).
 15. A drive systemaccording to claim 14, wherein said hydraulic drive pump (52) isconnected through a hydraulic circuit to a hydraulic motor (54).
 16. Adrive system according to claim 7 or claim 15, wherein said hydraulicdrive motor (54) is a variable capacity motor.
 17. A drive systemaccording to claim 7, claim 15 or claim 16, including a plurality ofhydraulic motors (17) and means (16) for connecting the motors into thehydraulic circuit individually, in series or in parallel to adjust thegearing effect of the drive system.
 18. A bicycle having a drive systemas claimed in any one of the preceding claims.
 19. A bicycle accordingto claim 18, including a hydraulic drive train that includes at leastone hydraulic motor for driving one or both wheels of the bicycle.